Transit orientation and azimuth readings: If a transit is oriented by setting Vernier A to the back azimuth of the previous line, taking a back sight, and then rotating to the forward station, what will Vernier A read?

Introduction / Context:
Precise traverse work relies on careful orientation of the transit (theodolite). One standard method is to set the plate reading to the known back azimuth of the previous line and sight the back point. Understanding what the vernier reads when subsequently sighting the forward station avoids confusion in azimuth-based traverses.

Given Data / Assumptions:

• Vernier A is set initially to the back azimuth of the previous line.
• A backsight is taken on the previous station to align the instrument.
• The telescope is then rotated to sight the forward station.

Concept / Approach:
If the transit circle is set to equal the back azimuth while sighting the back point, the instrument is oriented to the reference meridian. Rotating the telescope to the forward point changes the vernier reading to the azimuth of the forward line directly because azimuths are measured clockwise from the reference meridian and the orientation has been transferred to the plate reading.

Step-by-Step Solution:

Verification / Alternative check:
Repeat in reverse: if set to forward azimuth and fore-sight the forward point, a backsight to the previous point yields the back azimuth—confirming symmetry.

Why Other Options Are Wrong:

• Bearing may differ from azimuth depending on system (quadrantal vs whole-circle).
• The back bearing of the forward line would be read if sighting opposite direction.
• 360° − azimuth results from reading on the opposite face or different zero reference.

Common Pitfalls:
Mixing whole-circle bearings with azimuths; failing to clamp correctly before rotating; ignoring face-left/face-right conventions.

Final Answer:
Azimuth of the forward line